In the past, in order to remove air bubbles and foreign matters from the periphery of an ink ejection port of an ink jet head, there is an ink jet recording apparatus that circulates ink in the ink jet head. In such an ink jet recording apparatus, the ejection of the ink from the ink jet head is unstable unless the pressure near a nozzle is kept at a proper value. As a result, the quality of an image printed on a sheet is deteriorated, for example, density unevenness occurs.
In order to circulate the ink in the ink jet head while keeping the pressure near the nozzle at the proper value, the ink jet recording apparatus has a configuration explained below. As an example, a tank configured to store the ink to be supplied to the ink jet head includes a mechanism in which a weight is hung from bellows. The capacity of the internal space of the tank is variable according to the operation of the bellows. Therefore, the tank having the bellows passively suppresses fluctuation in pressure generated in the internal space. As another example, the ink jet recording apparatus can include a mechanism configured to actively control the pressure near the nozzle to the proper value.
However, in the configuration explained above, the flow rate of the ink circulating in the ink jet head depends on the weight applied to the bellows. Therefore, the flow rate of the ink cannot be changed. Consequently, if foreign matters that cannot be completely flushed down at a normal flow rate are caught in the ink jet head, the foreign matters cannot be removed.